One method of insulating and environmentally protecting a connector for a power cable or other cable is by use of a contractible insulating tube expanded to fit over the outer surface of a hollow cylindrical core. The tube and core are slid over one cable end and the cables connected by means of the connector. The tube and core are then repositioned over the connector area and the hollow cylindrical core is pulled out so that the expanded insulating tube may contract into contact with the connector and cables.
U.S. Pat. No.3,515,798, assigned to the assignee of the present invention and incorporated by reference herein, describes a one-piece, rigid, plastic core having interconnected adjacent coils in a closed helix configuration. One end of the core is partially unwound and led back through the core so that pulling on this end will cause the core to unwind and allow the tube to contract. Because the core is helically wound, the core length as it is extracted through the space between the core and the object over which the core has been positioned must be rotated around the object as the core end is pulled. This is cumbersome and does not permit the use of automation to remove the core as the machine cannot release the core on one side of the object and regrasp it on the other side of the object.
Japanese Utility Model Unexamined publication No. 3-28387 describes a straight pull-out core which overcomes the aforesaid drawback. The core, however, poses problems in that the core ribbon to be broken when pulled out straight is secured with multiple thin ribs. Therefore, when a tightening force is increased due to contraction of a rubber elastic body mounted on the core or an ambient temperature rises, the material strength is lowered, and thus the shallow ribs may break and crush the core. When the ribs are made thicker to increase the strength, the core ribbon becomes harder to pull out, and this deteriorates the workability.